1. Field of the Invention
The present invention generally relates to loading mechanisms, drive units, and information processing apparatuses, and more particularly to a loading mechanism for loading an information recording medium in a predetermined position and unloading the information recording medium from the predetermined position, a drive unit including the loading mechanism, and an information recording apparatus including the drive unit. The drive unit may be an optical disk drive unit for recording data on, reproducing data from, or rewriting the data of an information recording medium (hereinafter referred to also as an optical disk or simply as a disk).
2. Description of the Related Art
Recently, the digitization of information apparatuses and the accompanying rapid development of multimedia apparatuses have caused an increase in the amount of information (data) processed. This requires information recording media to have an even larger capacity.
Therefore, computers, audio equipment, and visual equipment have come to employ compact disks (CDs) and digital versatile disks (DVDs), which have the same disk diameter as the CDs but can record seven times as much data.
Disk drive units for recording data and reproducing data from these recording media can record information including data, audio information, and visual information on a recording medium by forming mark and space regions on the surface of the recording medium. Further, the disk drive units can read information recorded on the surface of a recording medium by emitting a laser beam onto the surface of the recording medium while the recording medium is being rotated at high speed, detecting light reflected from the surface, and converting the detected light into an electrical signal.
Normally, the disk drive unit includes a loading mechanism for positioning a disk at a position where data can be read from or written to the disk by transporting the disk to the inside of the disk drive unit after placing the disk on a tray pulled outside the disk drive unit.
In a conventional (optical) disk drive unit, when an optical disk is set inside the drive unit or extracted therefrom, first, a drawer-like tray for transporting the disk is slid and ejected from the loading base (frame) of the drive unit. This operation is hereinafter referred to as “tray unloading.” At this point, most of the tray protrudes outward from the loading base.
Thereafter, when a user places or removes the disk on or from the tray, and operates the drive unit or an apparatus such as a personal computer connected to the drive unit, the tray is slid in the reverse direction and pulled inside the loading base (hereinafter, this operation is referred to as “tray loading”) to be transported to a predetermined position inside the drive unit.
FIGS. 1 through 5 are schematic diagrams showing a conventional optical disk drive unit for providing a simplified description of its mechanism and operation. FIG. 1 is an exploded perspective view of the drive unit, which is disassembled into a loading base (frame) 2, a damper 11, and a tray 100. FIG. 2 is a top plan view of the loading base 2. FIG. 3 is a bottom plan view of the tray 100. FIG. 4 is a cross-sectional view of the loading base 2 to which the tray 100 is attached. FIG. 5 is a top plan view of the tray 100 and the loading base 2 in a tray-unloaded state, where the tray 100 is unloaded from (extended from or exposed outside) the loading base 2.
Referring to FIG. 1, the substantially circular damper 11 is attached to the upper parts of the X1 and X2 sides of the loading base 2 through a substantially rectangular damper holder 10 and an attachment part (not shown in the drawings).
A circular concave part 101 for receiving an optical disk (not shown in the drawings) and an elongated hole 102 having a rounded end in the Y2 direction and a squared end in the Y1 direction are formed in the center part of the tray 100. Further, a step part 105 is formed on each side part of the tray 100 extending along the Y-axis.
The substantially box-shaped loading base 2 has an open side in the Y2 direction. The tray 100 is attached to the loading base 2 so as to be slidable so that part of the tray 100 can be extracted from and retracted in the loading base 2 through its Y2 open side.
As shown in FIGS. 1 and 2, a tray driving mechanism 7 composed of a loading motor 71, a belt 72, a pulley gear 73, an intermediate gear 74, and a gear 75 is provided in the vicinity of the Y2 open side of the loading base 2. Further, a traversing mechanism 8 including a spindle motor 9 to which a turntable 91 is attached and an optical pickup 12 is provided in the center of the bottom of the loading base 2.
A plurality of rails 5, which are linear projections parallel to the Y-axis, are provided on each side on the bottom of the loading base extending along the Y-axis. Further, a plurality of tray holders 6, which are claw-like projections, are provided in a line on the surface of each inner wall of the loading base 2 along the Y-axis.
As shown in FIGS. 3 and 4, a rail groove 103 is formed on each side end (the opposite side of each step part 105) of the bottom surface of the tray 100 along the Y-axis. Each rail groove 103 includes an outer linear projection 131, a groove part 132, and an inner linear projection 133 all parallel to the Y-axis. The rail grooves 103 engage the rails 5 of the loading base 2 so that the tray 100 can slide on the rails 5.
Further, a saw-toothed rack 104 is provided to the inner linear projection 133 of one of the rail grooves 103 (the X2-side rail groove 103 in FIG. 3) so as to face inward (toward the other rail groove 103) to engage the gear 75 (pinion) of the tray driving mechanism 7.
According to this optical disk drive unit, the loading motor 71 rotates at the time of tray loading and unloading, and transmits its rotation to the rack 104 of the tray 100 via the belt 72, the pulley gear 73, the intermediate gear 74, and the gear 75 so as to slide the tray 100 in the Y1 and Y2 directions.
In the case of tray loading, the tray 100 in the unloaded state of FIG. 5 is pulled inside the loading base 2, and thereafter, the traversing mechanism 8 is raised up to the position of the damper holder 10 so that the damper 11 and the turntable 91 of the spindle motor 9 are in forced contact with each other.
On the other hand, in the case of tray unloading, the traversing mechanism 8 is lowered to its position shown in FIG. 1, and thereafter, the tray 100 is ejected outward from the loading base 2 as shown in FIG. 5.
The tray holders 6 prevent the tray 100 from being lifted up a predetermined distance or more from the bottom of the loading base 2, thereby preventing the tray 100 from disengaging from the loading base 2.
However, this type of optical disk drive unit develops trouble easily if an impact (external force) is applied to the tray 100 when the tray 100 is ejected from the loading base 2 as shown in FIG. 5.
Therefore, some conventional optical disk drive units, when sliding and ejecting the tray, disengage the gear driving the tray from a rotation body that raises or lowers the traversing mechanism in conjunction with the rotation of the gear. As a result, in those conventional drive units, the rotation body remains totally unaffected even if the ejected tray is forcibly stopped, pushed, or pulled. That is, in those conventional drive units, even if an impact is applied to the ejected tray from its front direction (the Y2 direction in FIG. 5), this only results in the tray being retracted inside the drive unit without damage to the gear or the rotation body. Japanese Laid-Open Patent Application No. 10-188421 discloses such a conventional drive unit.
The above-described conventional drive units, however, cannot prevent failure from occurring if an impact is applied to the tray ejected from the loading base from its sideward directions (the X1 and X2 directions in FIG. 5).
This is because if the tray in the ejected state receives an impact from the sideward directions of the disk unit, the tray may deform so as to have its rail grooves disengaged from the rails of the loading base.
Referring to FIG. 5, if an external force Fa or Fb is exerted from the sideward (X2 or X1) direction on the tray 2 ejected from the optical disk drive unit, torque is exerted on the tray 2 about a fulcrum Pa or Pb that is the furthest one of the rails 5 in the Y2 direction. As a result, a load is applied to the rear (Y1-side) edge Ea or Eb of the tray 2. If the point of application of the external force Fa or Fb is substantially the front (Y2-side) end of the tray 2 and the impact force is great, the rear part of the tray 2, which is thin as a general rule, becomes bent so that the rail groove 3 disengages from the rail 5 at the rear end Ea or Eb. Once the rail groove 3 disengages from the rail 5, it is impossible to perform tray loading and unloading operations.
In the conventional optical disk drive unit, when an external force such as an impact is exerted on the ejected tray at the time of tray unloading, the tray is supported at approximately one or two points on the loading base. If an external force is applied to the front end of the ejected tray, a high stress is exerted on the supporting part(s) by the moment. As a result, the tray may disengage from the engagement part of the loading base, and in the worst case, the tray may be broken. In any case, it becomes impossible to perform tray loading and unloading operations, thus causing great trouble to users.
FIGS. 6A and 6B are diagrams showing other configurations of the loading mechanism. The loading mechanism of FIG. 6A includes a tray 80 and a tray holding member (hereinafter referred to as a “frame”) 50. In this case, a pair of groove parts 80c and 80d are formed on the X2- and X1-side ends of the tray 80, respectively, so as to extend along the Y-axis. A plurality of cylindrical projections (bosses) 54 and a plurality of cylindrical projections (bosses) 54′ are formed on the frame 50 at predetermined intervals along the Y-axis so as to correspond to the groove parts 80c and 80d, respectively, of the tray 80. With the groove parts 80c and 80d engaging the bosses 54 and 54′, respectively, of the frame 50, the tray 80 can move back and forth along the Y-axis using the bosses 54 and 54′ as guides for the groove parts 80c and 80d. In this case, for instance, it is sufficient that only the bosses 54 remain in contact with the corresponding groove part 80c. There is often a space between the bosses 54′ and the groove part 80d. 
On the other hand, in the loading mechanism of FIG. 6B, as is opposite to the loading mechanism of FIG. 6A, a plurality of cylindrical projections (bosses) 180a and 180a′ are formed on the tray 80′, while guide grooves 354 and 354′ are formed on the frame 50.
A rapid spread of information equipment in recent years has increased the number of opportunities for those users who are not necessarily experienced in handling information apparatuses to use them. Further, there is also a continuing rapid increase in the number of opportunities to use information apparatuses at home. Therefore, there are more opportunities for children to use information apparatuses. In these cases, a wrong use of the drive unit or unintentional contact with the drive unit by the user may cause a great external force to be exerted on the tray ejected outside the drive unit. It is desirable that the drive unit operate normally without developing any trouble even in these cases.
In the ejected state, the tray is required to be in contact with the frame (projections) at least at two points. The conventional drive unit is designed so that the number of bosses that come into contact with the grooves formed on the tray in the ejected state is minimized (that is, two) in consideration of vibration generated by the movement of the tray.
However, if an external force is exerted on the ejected tray held only by the two cylindrical bosses, a great (surface) pressure is exerted on the contact points of the tray and the frame (bosses) because the area of the contact points is small. As a result, concave plastic deformations may be generated following (affected by) the shapes of the bosses, or the bosses formed on the frame may be broken.
In recent years and continuing, the below-described measure is generally taken to reduce the plastic deformation and the breakage of bosses. That is, by providing bosses 454a (FIGS. 7A and 7B) and 454b (FIG. 7B) each being substantially an elongated circle in a plan view (when viewed from the Z1 direction as in FIG. 7B), the area of contact between the tray and the frame (bosses) is increased so as to reduce the pressure applied to the contact points when an external force is exerted thereon.
In such a case, however, the area of contact between the tray and the frame (bosses) becomes large at the time of driving the tray so as to increase sliding resistance. This may result in problems such as a shortened useful service life of the entire loading mechanism and an increase in power consumption due to a large load on the tray-driving motor.